Since D-Sub VGA port can only carry an analogue signal, and HDMI is digital, you need an active adapter which converts the digital output to analogue input for your monitor - - - your existing adapter is most likely not an active one which is why it doesn't work since it doesn't do any signal conversion.
DVI-D also needs an active adapter since it's digital output only.
DVI-I doesn't need an active adapter since it can output both analogue and digital, so a non-active adapter is sufficient.
However, I do not know whether the GT 1030 is DVI-D or DVD-I - - so I can't help you there. If I had to guess I'd say it was DVI-I, but specs sheet on Geforce website doesn't specify which.